decay

• Decomposition is the process by which dead organic matter is broken down into simpler organic or inorganic substances.

  • For example, carbon dioxide, water, minerals, and simple sugars.

  It is essential for the recycling of elements throughout an ecosystem.
• Decomposition is carried out by two groups of organisms;

  • Detritus feeders (detrivores)
  • Decomposers
• Detritus feeders are small animals like worms and woodlice that feed on dead organic matter.
• Decomposers are microorganisms, such as bacteria or fungi.
• Factor that affects the rate of decomposition;

  • Oxygen availability.

  The higher the oxygen, the more aerobic respiration.

  • This means that more energy is available, so there is faster growth and decomposition.
• Factor that affects the rate of decomposition;

  • Temperature.

  A higher temperature causes particles to have more kinetic energy and enzymes are closer to the optimum temperature.

  • This means there is a higher rate of reactions so there is more decomposition.

  However, if the temperature rises too high the enzymes will denature which decreases the rate of reaction and, therefore, the rate of decomposition.
• Factor that affects the rate of decomposition;

  • Water content.

  Decomposers need water to survive, so the rate of decomposition increases in moist conditions.

  • However, if the soil becomes waterlogged then oxygen levels will fall which will decrease the rate of decomposition.
• Compost is a mixture of decayed organic material that is used to fertilise and improve the soil.
• Compost is prepared by leaving dead plant waste in ideal conditions (plenty of oxygen, warm, moist) until it is mostly decomposed.

  • It can then be spread across soil, where it provides nutrients for the plants.
• The mixture of gases anaerobic decay produces is known as 'biogas' and the most important gas is methane.
• When methane is combusted (burned), it releases a lot of energy which can be used for cooking, heating, or generating electricity.
• Biogas generators are large containers in which animal or plant waste is left to decay anaerobically.

  • It is important that there is no oxygen because if there is oxygen, the microorganisms will respire aerobically and produce less methane.

  Once the biogas is removed from the tank, a slugy material is left over, which contains a high density of useful minerals.

  • This can be spread on fields like fertiliser.